1. Field of the Invention
The present invention relates to a method and a device for measuring the activity of domestic animals comprising an automatic transfer of measurement results to a central evaluation station.
2. Description of the Prior Art
Identification systems for domestic animals comprising a passive transponder unit attached to an animal have been widely used and the constructional details thereof have been elaborated. See e.g. U.S. Pat. Nos. 4,510,495, 4,247,758 and 4,618,861, and the International patent application having publication number WO 91/11678.
In U.S. Pat. No. 4,510,495 a remote passive identification system is disclosed using a transponder responding to signals from a power transmitter. The animal identification and estrus detection system of U.S. Pat. No. 4,247,758 uses a transponder, that is a passive unit, which is interrogated and then transfers information of the number of movements of the animal. In the estrus detection system of U.S. Pat. No. 4,618,861 also a transponder is used, that obtains data from a self-powered motion sensor. Thus these two latter patents rely upon a transponder unit such that the animal estrus information about a particular animal can only be recorded when the animal passes near a transponder reader. For detecting estrus, the motion activity is determined or the fact whether the motion activity of the domestic animal has increased drastically is determined. Information of the result of the determination is communicated together with identification information for identifying the animal.
An estrus detector using such method is also disclosed in the European patent having publication number EP-B1 0 087 015, but here an estrus detection tag is used, that is self-contained having a visual indication and no remote information transfer. Such a visual indication can be missed or not seen during a critical period. A similar self-contained estrus detector is also disclosed in U.S. Pat. No. 4,895,165 but there the general motion activity of the animal is not monitored.
In the European patent application having publication number 0 549 081 measurements of the activity of an animal are made by means of an implanted device powered by an internal electrochemical battery and comprising a motion sensor and a temperature sensor providing signals. The signals can be processed by a processor having a memory in the device to give some characteristic value. This can be made by storing successive measurement signals until a certain number of signals has been collected. Then the stored values are used for determining a characteristic value that is again stored, the used values being eliminated from the memory. Such characteristic values are stored during a time interval and are then transmitted. The length of the time interval can be determined by the time at which the animal is in the direct vicinity of a reception device. For storing successive measurement signals a substantial memory is required drawing a corresponding amount a electric power. The processing of signals inside the device requires a considerable amount of electric energy.
In the published International patent application having publication number WO 95/32616 an electrochemical battery is used as a power source for the transmission of a signal indicating that the motion activity has increased. This design provides advantages such as a larger obtainable range for the transmitted signal. A disadvantage therein is that transmission is made only once and that it is not made sure that the signal is received by a centrally located station, for reasons such as the limited range of the transmitter, the fact that the animal can be at an unsuitable location when the transmission is made, etc. The transmitter of these data can also become non-operative and this condition will not be detected in this prior construction.